Angkor (of the Khmer culture) covered more than 160 square kilometers in northern Cambodia, situated on the edge of the Great Lake (Tonle Sap). The Classic Angkor civilization was part of the Khmer culture (between AD 802 and 1327). Prior to AD 802 the Khmer political landscape consisted of a number of independent kingdoms (Coe, 2003). Angkor became the imperial capital of the Khmer Empire. Ancient Angkor was a vast complex of temples built from the 8th to the 13th century AD. Angkor has been referred to as the world’s first mega city and a hydraulic city. A study by Evans, et al (2007) concluded that the area of Angkor’s urban complex was roughly 900 to 1,100 square kilometers which is almost four times the size of present day New York City. Angkor was a low density city with dwellings and water tanks spread over the area and connected by roads. Angkor is located in the Lower Mekong Basin which is subject to an annual cycle of monsoons causing alternation between a wet rainy season (summer monsoon) and a strongly marked dry season. The heavy rainfall during the summer monsoon causes the Mekong River and its tributaries to rise and flood low-lying areas. Snow melt in Southwestern China and Tibet flowing down the Mekong contribute to the flood volume. The Tonle Sap River, a tributary of the Mekong, reverses flow because of the back water effects from the large flows in the Delta of the Mekong and causes the water levels in the Great Lake (Tonle Sap) to rise. Floods subside during the winter monsoon and again river flow is toward the Delta causing the water levels in the Great Lake (Tonle Sap) to lower. Total rainfall in the Lower Mekong Basin fluctuates from year to year and is never very high, with an average of 150 cm per year in area of Angkor. In Phnom Penh the mean rainfall is 143 cm and can be as high as 231 cm and as low as 97 cm.

IDL TIFF file

The simulated natural color image was acquired on February 17, 2004, by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite. It is centered near 13.4 degrees North latitude, 103.9 degrees East longitude, and covers an area of 22.4 x 29.9 km. In this image, water is black and blue, vegetation is bright green, and bare earth is pink. Satellite of Angkor (Courtesy of NASA) The Angkor Wat temple complex is visible in the above image as the small black frame just below the image center. North of Angkor Wat is the larger square of Angkor Thom, the inner royal city built in the 12th century. The now dry moat around Angkor Thom is still visible as a pale pink square cut through the surrounding green vegetation. Within the square is a palace, homes for priests and government officials, and government administration buildings. West of Angkor Thom is the vast Western Baray, a reservoir built in the 11th century. The earthen walls constructed to hold water form a perfect rectangle, oriented exactly east-west. Possibly the Western Baray and its predecessor, the Eastern Baray, were built to provide water to the city, control water levels on the Siem Reap River, and provide irrigation water to the surrounding plain. The smaller Eastern Baray is also visible in this image. (Adapted from NASA) Map of Angkor showing surface features such as topography and waterways. (Modified figure courtesy of NASA with print added)

Barays The ability to store water was accomplished by constructing large reservoirs called barays. These reservoirs had inlet and outlet control structures so that they were used both in the time of drought and flooding. There were four large barays which had the respective approximate storage volumes (Coe, 2003): West Baray (48 million m3), East Baray (37.2 million m3), Preah Khan (Jayatataka) Baray (8.7 million m3), and Indratataka Baray (7.5 million m3). The approximate surface areas of these barays are West Baray (16 million m2), East Baray (12.4 million m2), Jayatataka Baray (2.9 million m2), and Indratataka Baray (2.5 million m2). The West Baray even holds water today. All of these barays may not have been functional at the same time, but one thing is for certain the water management system including the barays and other water infrastructure such as moats, canals, etc. required constant maintenance. A vast canal system was built that was used for both irrigation and transportation.

Angkor Wat Angkor Wat is the world’s largest religious monument. it has been referred to as a pyramid of three levels with each side enclosed by a well developed gallery of with four gopuras and corner towers, and crowned by five towers in a quincunx (Freeman and Jacques, 2013).

Satellite photo of Angkor Wat inside the moat (Courtesy of NASA)

At entrance Entrance/bridge to Angkor Wat. Entrance to Angkor Wat is from the West as compared to the other temples which have the entrance from the East. Moat surrounding Angkor Wat showing bridge. The moat defines the outer limits of Angkor Wat, which has walls faced with laterite and sandstone. Reservoir along entrance to Angkor Wat showing pond on left side (to the north) of the entrance walkway Reservoir along entrance to Angkor Wat showing reservoir on right side (south side) of the entrance walkway Stone basin on second level of Angkor Wat On the second level of Angkor Wat there were four stone rectangular basins (one shown above) in the cruciform cloister. These basins were most likely made water proof using a layer if clay. Model of Angkor Wat at the Grand Palace in Bangkok, Thailand

Neak Pean

Preah Khan Preah Khan entrance Moat Preah Khan baray Preah Khan baray

Ta Prohm Entrance to Ta Prohm

Sras Srang

Two photos below are of Sras Srang, a large reservoir. Sras Srang

Angkor Thom Elephant’s Terrace

The Bayon is situated at the center of the Angkor Thom. Remains of bridge near Siem Reap River Above two photos are of a bridge at Angkor

References

Acker, R (1998) New geographical tests of the hydraulic thesis at Angkor, South East Asia Research¸6(1), pp. 5-47.

The Hohokam and the Chaco regional systems stand out as two of the major prehistoric developments in the American Southwest. These two systems expanded over broad geographic areas of similar size (the Hohokam in Arizona and the Chacoans in New Mexico). These systems were of the similar time period but seemed to have developed and functioned independently, with little interaction. The Chaco and the Hohokam systems evolved in quite different environments, having considerably different irrigation infrastructure.

The Hohokam people inhabited the lower Salt and Gila River valleys in the Phoenix area in Arizona. These Hohokam Indian canal builders were given the name later by the Pima Indians. Even though the Indians of Arizona began limited farming nearly 3,000 years ago, the construction of the Hohokam irrigation systems probably did not begin until a few centuries C.E. It is unknown who originated the idea of irrigation in Arizona, whether it was local technology or introduced to them from cultures in Mexico.

Around 1450 C.E., the Hohokam culture declined, possibly because of a combination of factors: flooding in the 1080s, hydrologic degradation in the early 1100s, and the recruitment of labor by the surrounding population. A major flood in 1358 ultimately destroyed the canal networks, resulting in movement of the people. Canal use was either quite limited or entirely absent among the Pima Indians, who were the successors to the Hohokams Indians. The prehistoric people who lived outside the Hohokam culture area also constructed irrigation systems, but none was of near the grand scale as the Hohokam irrigation systems.

Around 900 C.E., the Anasazi of northwestern New Mexico developed a cultural phenomenon that now has more than 2,400 archaeological sites with nine towns each with hundreds of rooms along a 5.6-kilometer (9-mile) stretch. The Chacoan system is located in the San Juan basin in northwestern New Mexico. This basin has limited surface water, with most surface discharge from ephemeral washes and arroyos. The water collected from the side canyon that drained from the upper mesa top was diverted by either an earth or a masonry dam near the month of the side canyon into a canal. These canals averaged 4.5 meters (about 15 feet) wide and 1.4 meters (more than 4 feet) deep and were lined in some areas with stone slabs and bordered in other areas by masonry walls. These canals ended at a masonry head gate. Water was then diverted to the fields in small ditches or into overflow ponds and small reservoirs.

Chaco Canyon wash with mesa tops in background.

Architecture

Chaco Canyon, situated in the San Juan Basin in northwestern New Mexico, had limited surface water, most of which was discharged from ephemeral washes and arroyos. The Chacoans developed a method of collecting and diverting runoff as previously discussed. The diversion of water from the mesas into the canals combined with the clearing of vegetation resulted in the eroding (cutting) of deep arroyos to depths below the fields being irrigated. By ca. 1000 AD the forests of pinon and juniper trees had been deforested completely to build roofs, and even today the area remains deforested. Between ca. 1125 and 1180 AD, very little rain fell in the region. After 1180, rainfall briefly returned to normal. Another drought occurred from 1270 to 1274, followed by a period of normal rainfall. In 1275, yet another drought began which lasted 14 years.

Mesa Verde

The Ancestral Puebloan people made what is now known as Mesa Verde (Mesa Verde National Park) in southwestern Colorado their home for over 700 years, from 600 to 1300 AD. Today, Mesa Verde National Park preserves this ancient culture with over 4,000 known archeological sites including cliff dwellings and the mesa top sites of pit houses, pueblos, masonry towers, and farming structures.

Mesa Verde National Park, southwestern Colorado

Cliff dwelling at Spruce Tree House in Mesa Verde National Park

Four reservoirs have been identified in Mesa Verde National Park: Far View Reservoir (950 – 1180 AD); Morefield Reservoir (750 – 1100 AD); Sagebrush Reservoir (950 – 1100 AD); and Box Elder Reservoir (800 – 950 AD) (Wright, 2006). Far View Reservoir (also known as Mummy Lake), located in Chapin Mesa, was built during two different periods and was used to store water for domestic uses. Reservoir dimensions are about 90 feet (27 m) in diameter and 12 feet (3.6 m) deep (with a depth of water storage of about 4.6 ft). This reservoir structure (shown below) contains masonry work, a diversion ditch (inlet structure), and channels. The restored inlet structure is also shown in the figure below.

Remains of Far View Reservoir at Mesa Verde National Park.

In the foreground is the restored intake structure (canal) into the reservoir.

Restored stairway at Far View Reservoir in Mesa Verde National Park. Stairway not only funcitoned as a way to the stored water but also may have had special social or religious function.

Gerasa is approximately 30 miles north of Amman in modern-day Jordan. The city, also known as Antiocha on the Chrysorrhoas during the Helenistic times. Gerasa was founded by Antiochus IV Epiphanes (175-164 B.C.). Gerasa is divided by the Chrysorrhoas River. Ancient ruins of the eastern part has been covered by the present-day town was most likely the residential part of Gerasa. The western part was the heart of the city where the Temple of Artemis was located along with many monumental structures.

Colonnadad avenue with the monumental columns crowned by Corinthian capitals. Several stormwater inlets are located along the street.

Nabataean Petra began around 300 BC from nomadic settlement origins. The city was also occupied starting around 106 AD with final occupation to the 7th century AD. Petra location was located between Egyptian, Babylonian, and Assyrian territories. As a result over time many exterior cultural, political, and technological influenced the history of the Nabataean City. The Nabataean kingdom included Jordan, the Hawran in southern Syria, Sinai, the Negev, a large part of the Hijaz in north-western Arabia, and for a short time it even included Damascus. The verb “nabat” in Arabic means for water “to percolate from underground to the surface.”

Petra’s location as an intersection for caravan trade from Arabia, Africa, and the Far East sustained the life and wealth of the city and allowing appropriate water supply infrastructure for its survival as a result of the complex topography and the limited water resources of the area. Water infrastructure technology passed on through the ages obviously from the Egyptian, Mesopotamian, Minoan, Hellenistic Greeks, and the Romans, Petra was able to develop magnificent water infrastructure for the arid area. The Nabataeans had a tremendous understanding of the natural flow of water in the unique surroundings. Water infrastructure included terraces, channels, settling basins, aqueducts, dams, rainwater harvesting, flood harvesting, groundwater harvesting, a large range of size and types of cisterns, reservoirs created by dams, water distribution tanks, and springs. Throughout the Petra area there are hundreds of cisterns.

The Treasury (Al Khazna)

Road to entrance along Wadi Musa

Near entrance along Wadi Musa

At entrance showing new additions for diverting flows from the Siq and the ancient tunnel built by the Nabataeans for diverting flows from the Siq

Entrance to Siq where Wadi Musa originally flowed.

Flood bypass tunnel built by the Nabataeans near entrance to the Siq from Wadi Musa into Wadi Mudhlim through the tunnel W. Bachmann’s 1917 reconstruction of the entrance to the Siq with the plan above and the elevation above. Also shown is the location of the flood bypass tunnel.

Aqueduct along Siq , which is Wadi Musa.

Outlet from cistern/settling basin

Wadi Qantara inlet with newly constructed dam structure in the background. Cross-drainage structure for water channel (aqueduct) is shown with the two outlets.

Wadi Qantara inlet showing the rock-cut steps to the sanctuary in the western cliff.

Aqueduct channel showing rock cover that once covered the aqueduct

Stilling basin in Siq at bottom of Wadi Jilf after restoration.

Shows stilling basin at outlet of Wadi Jilf. Two outlets in cross-drainage structure in background.

Settling basin along aqueduct in the Siq

View of aqueduct along Siq

Along Siq

Along Siq showing aqueducts on both sides.

At end of Siq is the Treasury (Al Khazna)

Steps of the path to the High Place of Sacrfice along Wadi Al-Mahfur

The High Place of Sacrifice. Notice the outlet on the right for cleaning the sacrifice area.

Small sacrifice area with drain and carved out area that could also collect water carved out chamber for storage of water.